At this point in his career, no, record sales should not bother us or him. He is never going to sell as many albums as Thriller or Bad, even if he comes out with an album that is better than them. No one ever will, the industry has changed too much since then.
However, they won't matter only if Michael acknowledges this publicly. He needs to be humble and honest about the fact that this album will be more like an Off The Wall for the 21st century (as we have heard), focused on the music rather than selling a s*** load of units. This way he will gain both critical acclaim, shut up the haters and give his fans some fantastic music that we all know he is still capable of.
To be honest, I would prefer a casually and naturally fantastic album by Michael that doesn't rely on too much on promotion rather than an attempt to drum up the popularity towards an unachievable height of Thriller or Bad.
It should be like: Heres the album. It's fantastic. Listen to it. Like it? Buy it. Don't like it? ***** you!
Plus the fact, any Michael Jackson album WILL sell well compared to any other artist in the same year... it's just a shame that people continue to compare the 2000s MJ to the 1980s MJ instead.